1. Field of the Invention
The present invention relates to detection of leaks. More particularly, the present invention relates to detection of oil leaks in pipes with electrical transmission piped-type cables.
2. Description of the Prior Art
Current installed leak detection systems for fluid pipe systems such as underground piped-type cables and others, use pressure decay and/or flow monitoring in order to determine if a leak exists. Leak Detection Systems for oil pipe systems such as underground piped-type cables and others, monitor the pressure in the pipe or oil tank to interpret pressure drops. In addition, in some cases the frequency of pressurization pumps starts is used as an indication of larger oil leaks. However, these systems often initiate false leak detection alarms when a heat source is removed, such as de-energizing the electric underground cable, resulting in fast cooling of the oil. This causes decreases the interrelated oil volume and pressure inside the oil pipe or tanks setting off the alarm. Other methods include systems which monitor the flow of oil in the pipes, such as underground piped-type cables and others, interpret the differences in flow at different pipe locations to detect leakages.
When the accuracy of oil tank level gages, flow meters, and temperature variations of the oil inside the pipe or tanks is taking into account, detecting leakages of oil becomes very difficult. Resulting in the detection of only large oil leaks as a result of prolonged small oil losses having accumulative effects, or more rapid oil loss having little drag effect.
Past attempts to compensate for the temperature changes of the oil inside the pipe or oil tanks, such as piped-type cables and other systems, face two (2) obstacles:
1. The temperature of the oil along the pipes, such as underground piped-type cables and other systems, typically varies along the pipe, and a large number of measuring devices is required in order to monitor oil temperature. This is not practical or economical. In addition, temperature monitoring along the pipe is very difficult and expensive for existing oil pipes. PA1 2. Small leakages are difficult to detect in existing leak detections systems due to the accuracy of the instrumentation used at the present time (instrument errors). This is more apparent when oil pipes, such as piped-type cables and other systems, may contain oil volumes ranging typically between 100,000 to 200,000 gallons. Even with the assumption that the calculated oil volume in the pipe is accurate, leak detection accuracy due to temperature effects and accuracy in the measuring instrumentation yields results with sensitivity that is unacceptable from the environmental point of view (500-1,000 gallons).
For actual electrical underground transmission systems, a traditional leak detection method consists of monitoring the amount of oil in the system by reviewing and comparing oil tank level readings that are recorded on charts recordings. These readings are taken continuously during seven day periods and then they are sent to an engineering office for further analysis. This way, the leaks are detected only after substantial accumulation of oil loss.
Numerous innovations for Leak Detection System have been provided in the prior art that are described as follows. Even though these innovations may be suitable for the specific individual purposes to which they address, they differ from the present invention as hereinafter contrasted.
In U.S. Pat. No. 5,410,255, titled Method and Apparatus for Detecting and Distinguishing Leaks Using Reflectometry and Conductive Tests, invented by Douglas S. Bailey, a method and apparatus for detecting and locating fluid leaks, particularly liquid leaks, and determining whether the leaking liquid being detected is non-conductive liquid such as hydrocarbon or conductive liquid such as water utilizes a composite detection cable having a pair of insulated conductors and a pair of un-insulated conductors. Pulses are applied to the insulated conductors and leaks are detected and located utilizing time domain reflectometry (TDR) techniques. The resistance between the un-insulated conductors is measured to determine whether or not the leak is conductive.
The patented invention differs from the present invention because the patented invention requires a special cable having a leak detecting cable embedded within the primary cable. Time Domain Reflectometery is used to detect the leak. The present invention measures one temperature at the output of a cable at a given pressure and the volume in a reservoir tank at the same time. A second temperature and volume measurement is made some time later at the same pressure. The changes in temperature and volume are compared to determine if a leak is occurring.
In U.S. Pat. No. 5,372,032, titled Pressurized Piping Line Leak Detector, invented by Ernest A Flippi and Kenneth L. Miller, a line leak detector system which does not require modifications to existing piping or installation. The system requires a controller and transducer and installs at existing fuel dispensers. The two components are connected by a length of electrical cable. The invention detects leaks in underground pressurized piping systems for fuel products and other incompressible liquids. The system performs three levels of leak detection, broken pipe, 3 gph and 0.2 gph. Existing piping systems variables relating to bulk modules, variable pump off pressure and thermal differential between fuel and piping with surrounding soil influence, are compensated for. The status of the leak test is reported by encoded lights and horn. In various combination of flash, blink and steady state lights plus chirp, or audible horn. The transducers and cable are intrinsic safe, permitting installation in hazardous environments. The system permits selection of functional modes, thereby making the system able to report leak status to existing underground fuel tank inventory systems.
The patented invention differs from the present invention because the patented invention measures only pressure changes compensated for temperature and bulk modulus. The present invention measures one temperature at the output of a cable at a given pressure and the volume in a reservoir tank at the same time. A second temperature and volume measurement is made some time later at the same pressure. The changes in temperature and volume are compared to determine if a leak is occurring.
In U.S. Pat. No. 4,570,477, titled Leak Detecting Cable, invented by Hiroyuki Sugibucti, a liquid leak detecting sensor in cable form is provided wherein an element of the cable material which is easily deformable and which on deformation, maintains the cable in deformed configuration.
The patented invention differs from the present invention because the patented invention requires a specially constructed cable that has a pair of sensing wires that sense the leakage of a conductive liquid. The present invention measures one temperature at the output of a cable at a given pressure and the volume in a reservoir tank at the same time. A second temperature and volume measurement is made some time later at the same pressure. The changes in temperature and volume are compared to determine if a leak is occurring.
In U.S. Pat. No. 4,480,251, titled Apparatus to Monitor Electrical Cables, Including Splice Joints and the like, of the ingress of Moisture, invented by John P. McNaughton, Wayne E. Domenco, and David E. Vickey, Apparatus for monitoring electrical cables for the presence of moisture within the cable along the full length of the cable and at specific points such as splices along its length comprised of a pair of dielectrically separated conductors arranged along a central station and remote stations along the length of the cable at the specific stations to be monitored. The remote stations each include a further dielectrically separated pair of conductors for sensing moisture at the point and signals along the first pair of conductors to the central station. The central station detects moisture by an increase in current in the conductors and also detects a signal from remote stations. Branch cables spliced into the main cable include dielectrically separated conductors also spliced into the main conductors with the remote station at the splice including means for disconnecting the branch cable conductors from the main cable conductor under control from a signal from the central station.
The patented invention differs from the present invention because the patented invention detects the presence of outside moisture inside a cable. The patented invention is not designed to function in conjunction with a liquid filled cable. The present invention measures one temperature at the output of a cable at a given pressure and the volume in a reservoir tank at the same time. A second temperature and volume measurement is made sometime later at the same pressure. The changes in temperature and volume are compared to determine if a leak is occurring.
In U.S. Pat. No. 3,981,181, titled Method of Detecting Liquid Leak and a Cable Therefor, invented by Sadamasa Ochiai in the method for detecting liquid leak of the present invention, the inventive cable, I.E. a parallel pair or a coaxial cable insulated with porous polymer material, is placed along or under a storage and/or transport means for conveying chemicals. If a leak occurs, the leaked liquid permeates into two conductors from each other, and varies the characteristic impedance of the cable to some detectable extent. The variation of impedance is electrically measured by a pulse reflection method (TDR). The invention method comprises; sending pulse waves from one end of the cable, sensing the reflected and deformed pulse shape, and thus detecting and locating the liquid leak.
The patented invention differs from the present invention because the patented invention utilizes a parrallel pair or a coaxial cable insulated with porous polymer material. If a leak occurs, the leaked liquid permeates into two conductors varying the characteristic impedance of the cable to some detectable extent. The patented invention requires a specially built cable. If a leak occurs, the leaked liquid permeates into two conductors from each other, and varies the characteristic impedance of the cable to some detectable extent.
Numerous innovations for Leak Detection System have been provided in the prior art that are adapted to be used. Even though these innovations may be suitable for the specific individual purposes to which they address, they would not be suitable for the purposes of the present invention as heretofore described.